Basis of presentation and significant accounting policies and practices - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Antidilutive securities excluded from computation of earnings per share, Amount (in shares)	2	3	3	4
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, carrying value	$ 7,739		$ 7,739		$ 6,798
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, estimated fair value	$ 8,430		$ 8,430